Method for adjusting the space between cathode and first plate grid electrodes in an electron gun member

ABSTRACT

IN AN ELECTRON GUN MEMBER, A METHOD FOR ADJUSTING THE SPACE BETWEEN THE ELECTRON BEAM EMITTING SURFACE PLATE OF THE CATHODE AND A FIRST PLATE GRID ELECTRODE HAVE A SUBSTANTIALLY ANNULAR PROTUBERANCE THEREON, COMPRISING THE STEPS OF PROJECTING LIGHT INTO A SPACE FORMED BETWEEN THE CATHODE AND FIRST PLATE GRID ELECTRODE THROUGH AT LEAST   ONE VOID AREA FORMED IN PART OF THE PROTUBERANCE, PRESENTING THE RESULTANT IMAGE OF SAID SPACE IN AN OPTICALLY MAGNIFIED FORM ON A SCREEN POSITIONED OUTSIDE OF THE ELECTRON GUN MEMBER, AND ADJUSTING AND DETERMINING THE SPACE WHILE MONITORING THE OPTICAL MAGNIFIED IMAGE.

June 6, 1972 ASAHIDE TSUNETA ETAL 3,667,824

METHOD FOR ADJUSTING THE SPACE BETWEEN CATHODE AND FIRST PLATE GRID ELECTRODES IN AN ELECTRON GUN MEMBER Original Filed May 6, 1968 2 Sheets-Sheet 1 June 6, 1972 ASAHIDE TSUNETA EPA!- 3,667,824 METHOD FOR ADJUSTING THE SPACE BETWEEN CATHODE AND FIRST PLATE GRID ELECTRODES IN AN ELECTRON GUN MEMBER Original Filed May 6, 1968 2 Sheets-Sheet FIG. '4

i L F FIG. 5

United States Patent "ice Int. Cl. Hillj 9/42, 9/44 US. Cl. 316-23 3 Claims ABSTRACT OF THE DISCLOSURE In an electron gun member, a method for adjusting the space between the electron beam emitting surface plate of the cathode and a first plate grid electrode having a substantially annular protuberance thereon, comprrsmg the steps of projecting light into a space formed between the cathode and first plate grid electrode through at least one void area formed in part of the protuberance, presenting the resultant image of said space in an optically magnified form on a screen positioned outside of the electron gun member, and adjusting and determining the space while monitoring the optically magnified image.

This is a division of application Ser. No. 726,765, filed May 6, 1968, now abandoned.

The present invention relates to a system for adjusting the space between the cathode and first plate grid electrode disposed adjacent to each other of an electron gun member and more particularly to a method adapted for an electron gun member used in color television picture tubes.

In known electron gun members, the plate grid electrode has an annular protuberance concentric with a fine aperture through which electron beams emitted from a cathode are carried, said protuberance being intended to increase the flexural strength of the grid electrode. Within a space surrounded by the annular protuberance is genenally disposed an electron emitting surface plate formed at one end of the cathode. Since the dimensions of the aforementioned space between the first plate grid electrode and electron emitting surface plate of the cathode largely affected the electrical properties of the electron gun member, it is desired that measurement of the dimen sions be made as accurately as possible. Practically, the tolerance for such errors of measurement in the space should be :15 microns.

With the prior art, the electron emitting surface plate of the cathode was completely surrounded by the aforementioned annular protuberance formed on the first plate grid electrode, so that it was impossible to observe the space between the electron emitting surface plate of the cathode and the first plate grid electrode. Accordingly, the conventional practice was to measure a static capacity between the first plate grid electrode and cathode, convert the measured capacity into electrical signals and determine the space indirectly from readings on an electric meter. With such electrical measurement, however, there often occured errors if any change took place in the shape, size and material of the first plate grid electrode and cathode, temperature of these members, ambient atmosphere, electrical correction of the measuring instrument and other factors. For instance, where measurement was made of a space ranging between 0.08 and 0.15 mm., errors of :30 microns were ordinarily realized, which far exceeded the desired tolerance of :15 microns. As a result, there could be put to practical use only 50 to 65 per- 3,667,824 Patented June 6, 1972 cent of all electron gun members manufactured by the prior art. Furthermore, the conventional method of measuring the space required an extremely complicated instrument.

Accordingly, an object of the present invention is to provide a method for adjusting the space between the cathode and first grid electrode of an electron gun member, which enables errors in the measurement of said space to be reduced to within the specified tolerance of :15 microns.

Another object of the invention is to provide a method for adjusting the space between the cathode and first grid electrode of an electron gun member and permitting said space to be accurately determined by simple apparatus and operations.

. SUMMARY OF THE INVENTION With respect to an electron gun member comprising an electron emitting surface plate disposed at the top end of a cylindrical cathode to form an electron emit ting plane, said surface plate being inserted into an annular protuberance provided on a first plate grid electrode coaxially arranged with said cylindrical cathode adjacent thereto and perforated substantially at the center with an aperture allowing the passage of electron beams, the method of the present invention consists in projecting light into a space between the cathode and first plate grid electrode through at least one void area formed in advance in part of the periphery of the protuberance, presenting the resultant image of said space in an optically magnified form on a screen positioned outside of the electron gun member, and adjusting and determining said space while monitoring the optically magnified image.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a section, taken on line I-I of FIG. 2, of one of three electron gun members assembled using an embodiment of the method according to the present invention for use in color television;

FIG. 2 is a section, taken on line 11-11 of FIG. 1, of the assembly of the three electron gun members;

FIG. 3 is a perspective view of the cathode and first plate grid electrode of the electron gun member;

FIG. 4 is a schematic representation of an embodiment of the method according to the present invention for measuring the space between the cathode and first plate grid electrode;

FIG. 5 shows the optically magnified images of the space between the cathode and first plate grid electrode projected on the screen of FIG. 4;

FIG. 6 is a section similar to FIG. 1 assembled using another embodiment of the method according to the invention; and

FIG. 7 is a perspective view of the first plate grid electrode used in FIG. 6.

There will now be described an embodiment of the method according to the present invention by reference to FIGS. 1 to 5. As illustrated in FIG. 1, the electron gun member 11 consists of a cylindrical cathode 12, a first plate grid electrode 13, a second and a third grid electrode 14 and 15 and a fourth grid electrode (not shown) coaxially arranged in the order mentioned. The cathode 12 and electrodes are secured in place by support legs 1619 which in turn are inserted into support rods 20 formed of insulating material. Three such electron gun members 11 are arranged in a triangular pattern as shown in FIG. 2 to form an electron gun assembly for color television. The first plate grid electrode 13 has a small aperture 22 perforated in approximately the center of a fiat segmental plate 21 as illustrated in FIG. 3. The aperture 22 is intended to pass electron beams from an electron emitting surface plate 24 fitted to the top end of arrannular protuberance 23* approximately concentric" with the aperture 22 (this protuberance need not be truly circular) and surrounding the electron emitting surface plate 24. The annular protuberance 23 respectively has two opposite void areas (or missing portions) 25 and 26 formed in its peripheral direction. The void areas should preferably be formed at least wider (for example,'2.0 to 3.0 mm.) than the diameter (for example, 1.5 to 2.0 mm.) of the cylindrical cathode. Both linear sides of the segmental flat plate 21 have a pair of support legs 17 bent substantially perpendicular to the horizontal plane of said fiat plate 21. The rear ends of the support legs 17 are set apart from each other to form a light passage window 27. Numeral 2 8 of FIG. 1 denotes a cylindrical support for the cathode 12.

, There will now be described the assembling of three electron gun members. Each unit of the fourth grid electrode (not shown), third, second and first grid electrodes -13 and a cylindrical cathode support 28 securely arranged from the top to the bottom in the order mentioned using a jig (not shown). Under such supported condition, all these components are fused to three glass rods to form an assembly of three electron gun members 11. Next into each cylindrical cathode support 28 is inserted a cathode 12. (Since these three electron gun members are of the same construction, there will hereinafter be described only one of them for convenience.) The top end of the inserted cathode is disposed in a space surrounded by the annular protuberance 23 formed on the segmental fiat plate 21 of the first plate grid electrode. 'In this case, as illustrated in FIG. 4, a light issued from a source 30 which directs a light toward the cathode 12 and the first plate grid electrode, for example, as indicated by the arrow of FIG. 2 passes through spaces between the component parts, a light passage window 27, a void area 26, a space 31 between the cathode and the first plate grid electrode, the opposite void area 25 and finally an optical lens 32, where the image of the space 31 is magnified 20 to 50 times. Then the image thus magnified is projected on a screen 33 disposed outside of the assembly of the electron gun members 11. The light from the source also passes between the first plate grid electrode 13 and the upper face of the support leg 16 and spreads out to illuminate the area surrounded by the glass rod 20 in much the same way as the area surrounded by the light passage window 27. Thus the operator can adjust the space 31 while observing an image cast on the screen 33 outside of the assembly of the electron gun members 11. Such adjustment can be carried out more accurately and easily than in the prior art, enabling errors in the measurement of the dimensions of the space 31 to be reduced to within the specified tolerance of :15 7

microns. The method of the present invention, therefore, elevates the yield of electron gun members for color television from the previous 50 to 65 percent to about 95 percent, and in consequence facilitates the manufacture of their assemblies.

There will now be described another embodiment of the method according to the present invention by reference to FIGS. 6 and 7. The parts shown in these figures which are substantially the same as those referred to in the preceding embodiment are denoted by the same reference numerals, and a description thereof is omitted. As already shown in FIG. 3, the preceding embodiment involved a first grid electrode 13 provided with an annular protuberance '23 having opposite void areas 25 and 26.

In the annular protuberance 40 of the first grid electrode 13 there is provided only one void area 41, as shown in FIG. 7, omitting any such parts as corresponding to the void area 2 6 shown in FIG. 3. The reason is that even if said void area 26 is not formed 'in the 'annular'protuberance 40, a light from the source can be fully introuced into the space surrounded thereby, thus enabling, as shown in FIG. 6, the space 31 between the top of the cathode 12 and the first grid electrode 13 to be observed simply by means of the void area 41. Accordingly, said space can be properly adjusted by the same means as used as used in the preceding embodiment.

We claim:

1. In a method of making an electron gun member comprising an electron emitting surface plate disposed at the top and of a cylindrical cathode to form an electron emitting plane, said surface plate being inserted into an annular protuberance provided on a first plate grid elec trode coaxially arranged with said cylindrical cathode adjacent thereto and perforated substantially at the center with an aperture allowing the passage of electron beams, said annular protuberance having at least onevoid area formed therein, a method for adjusting the spacing between the electron beam emitting surface plate of said cathode and said first plate grid electrode comprising the steps of; v

projecting light into a space between the cathode and first plate grid electrode through at least one void area formed in advance in part of the periphery of the protuberance;

presenting the resultant image of said space in an optically magnified form on a screen positioned outside of the electron gun member; and

adjusting and determining said spacing while monitoring the optically magnified resultant image of said space.

2. In a method of making an electron gun member according to claim 1, the method wherein said void area is formed wider than the diameter of said cylindrical cathode.

3. In a method of making an electron gun member according to claim 1 wherein at least two oppositely located void areas are formed in said protuberance, the method wherein said light is directed through one of said void areas and said resultant image of said space is presented on said screen through the opposite void area.

References Cited JOHN F. CAMPBELL, Primary Examiner R. B. LAZARUS, Assistant Examiner US. Cl. X.R.

4 UNITED STATES PATENT OFFICE IERTIFICATE OF CORRECTION Dated June 6 1 Patent: No 3 667 824 Inventor-(s) Asahide TSUNETA, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shewn below:

In the heading:

after "Asahide 'ISUNETA insert -Masakatsu NAKAHARA,

deceased, by Haruji Nakahara and Fusake Nakahara, legal representatives- Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOTTSCHALK Commissioner of Patents Attesting Officer 

